In exhaust gas aftertreatment for a vehicular internal combustion engine, the secondary air pump generally is switched on only briefly, particularly during the warming up phase of the internal combustion engine in order to burn the unburned fuel in the exhaust gas, which accumulated during cold starting. This means that the check valve in the air delivery pipeline is exposed more or less directly to the hot exhaust gases during the bulk of the operating time, so that the danger exists that it will leak or be destroyed in the course of time. Pressure fluctuations occurring in the exhaust system may also cause mechanical failures. In this case, hot exhaust gas can enter the air delivery pipelines and, under some circumstances reach the secondary air pump, thereby damaging it. Moreover, the air delivery-pipeline can burn through, as it consists, at least partly, of elastic material, since the secondary air pump is generally mounted on the car body and therefore has to be connected with the exhaust system by means of a flexible pipeline.